Optimal design and implementation of tunnelling magnetoresistance based small current sensor with temperature compensation

This paper proposes a tunnelling magnetoresistance (TMR) based current sensor considering temperature error compensation, for the measurement of current in the range from a few hundred micro-amperes to a few hundred mini-amperes, in the applications in power systems. Theoretic and simulation analysis are studied for the optimization design of the TMR based small current sensor in the perspective of the magnetic loop structure, magnetic core parameters, and secondary circuit. An improved temperature error compensation circuit is proposed to suppress the sensitivity drift of the sensor. A prototype is built to verify the proposed design. According to the experiment results, the proposed TMR small current sensor has a measurement range of ±200 mA and a sensitivity of 10 V/A. The temperature error compensation scheme can reduce the temperature coefficient of sensitivity of the sensor from 1780 ppm/°C to 504 ppm/°C. The proposed TMR small current sensor can measure small current effectively.